Many vehicles use steering or swing joints that employ two hydraulic cylinders disposed to steer or swing by moving in opposite directions. For example, one cylinder will extend while the other cylinder retracts, and the two cylinders acting together in opposite directions will together affect the desired steering or swinging.
One cylinder will affect the steering or swinging by pushing two members apart. The other cylinder will contribute to the same steering or swinging by pulling the two members together.
In these vehicles, the swinging and steering is typically limited to a restricted range of motion such as 90° to 180°. To prevent the swinging and steering from damaging the vehicles, mechanical stops are typically provided on the two members to prevent over-swinging or oversteering that would otherwise damage the vehicle.
One problem with this arrangement is that the impact of the mechanical stops banging together can damage the vehicle.
This problem has been somewhat ameliorated by reducing hydraulic fluid flow to the cylinders to slow the swinging and steering down. As the two members being swung/steered with respect to each other approach their mechanical stops, the pressure in the hydraulic cylinders is increased to decelerate and/or stop the swinging/steering before the stops collide.
One problem with this arrangement is that a position sensor must be provided to sense the approaching collision of stops and to signal an ECU to close the valves and slow and/or stop the swinging/steering.
This problem has been somewhat ameliorated by using hydraulic cylinders that have internal dampers. These dampers are built into the structure of the hydraulic cylinder and automatically throttle the hydraulic fluid flow, thereby generating high pressures in the cylinders that damps the swinging/steering as the cylinders approach their end-of-stroke.
One problem with these arrangements is a difficulty in keeping multiple cylinders with internal dampers synchronized. As the cylinders wear or come out of adjustment, the damping load can be shifted to one of the cylinders, thereby damaging it.
What is needed is an efficient, effective and cost-effective way to absorb the energy of swinging and steering and thus reduce or eliminate damage.